This lecture from Astrobiology and Space Exploration is entitled "Pushing the Envelope for Life."
In order to understand “where we come from”, we must understand the evolutionary history of life, and in order to understand that, we must understand the physical history of the earth, and in order to understand that, we must understand its history in the solar system, and in order to understand that….you get the idea. So, to start the course we will go all the way back to the origin of the universe. At the time of the Big Bang, words such as “biology”, “chemistry” and even “physics” had no meaning. Some of these unfolded in the first fraction of a second, some through generations of stars and time measured in billions of years. These numbers range from incredibly small to equally incomprehensibly large. The concepts in cosmology are often so far outside of our experience that it is hard to imagine where these numbers come from. An expanding universe 13.7 billion years old? Wow. For this reason, we will include epistemology – in other words, how we know what we do today.
The Big Bang created the physical universe. Of course life is part of this physical universe, but the immediate building blocks of life are chemicals. Before the Big Bang, words such as “time” had no meaning, but even in the first few minutes there could be no chemistry since there were no atoms. The nuclei of some of the lighter elements formed within minutes, atoms some time later, and elements heavier than lithium were forged in the supernovae of stars. Thus, we are primarily star dust, although the hydrogen atom you drink tonight may be nearly as old as the Big Bang. But living organisms are more than a collection of atoms. They are a cauldron of molecules in a solvent. For life on earth, that solvent is water. The building blocks of chemical compounds had to form other molecules as well, especially ones based on carbon. Where could these compounds have been formed? Were they formed on earth or transported from elsewhere? Most stunning are the recent discoveries in astrochemistry showing that the organic compounds that make up life on earth may possibly be THE language of the universe. Stay tuned.
A perennial favorite is the idea of time travel. What would happen if we could go back in time and alter the future a la “Back to the Future”? The great narrative of the history of life has a complexity rife with subplots and twists, many of which we will never uncover. Yet somehow the story of life on Earth began with a prebiotic ooze and ended with the awe-inspiring diversity of life we see today – including us. But like any story, the present was not inevitable, and neither is tomorrow. Seemingly small events have reverberated through the eons. If we take the story evolution and reset the clock to some arbitrary time, how much of the future could be predicted? Surely the details would be quite different, but could we predict anything? Is there such a thing as a law in evolution? What about some of life’s greatest hits, from the eukaryotic cell, to photosynthesis, multicellularity, intelligence and even us?